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• A later step could be to add Cm to the Am targets, and burn them in the same way; the waste
reduction factor would somewhat increase to 50, but the cost would also increase.
• Later on, and if the need is recognised, the reduction factor might be improved progressively
up to about 160, provided that the targets of minor actinides are reprocessed and recycled.
Such versatility is attractive. The needed R&D programme in support, engaged step by step, remains
at a moderate level.
6.5 Ways to reach 90% burn-up in targets
Research has been engaged on Am targets. Many European laboratories have started fabrication
and irradiation of such targets. In particular, the EFFTRA-T4 experiment with fabrication made at
ITU and irradiation in the HFR reactor at Petten, supported by other partners, has reached an Am
burn-up of 28% [7]. A problem was however raised by the large swelling of the spinel matrix, which
would not allow much longer irradiation. The EFFTRA partners are searching for improvements.
Among the possible solutions, a promising one is offered by the technology of Pu coated particle
fuel, as successfully experienced in the DRAGON experimental reactor [8]: this particle fuel did not
swell even after a 60% burn-up corresponding to almost complete depletion of the Pu. The adaptation
of this process to Am targets deserves therefore careful feasibility verifications.
Studies have just been started at BELGONUCLEAIRE and EDF to assess the possibility of an
adaptation of this type of fuel to Am targets, to make them resistant to the important build-up of gas
pressure related to helium and fission products, the goal being to effectively burn 90% of the Am
loaded.
7. Conclusions
This paper has underlined how attractive is the concept of putting Am, or Am + Cm targets on
special moderated positions of an EFR core. Their irradiation up to 90% burn-up seems feasible in a
long but still affordable irradiation.
It was shown by calculations that, if reprocessed and recycled, this target concept in a fast reactor
could lead, in a reactor park made of a mix of PWRs (UO 2
) and LMFRs, to an actinide waste mass
reduction factor of 100 or more.
If the targets can reach a 90% burn-up and are not further reprocessed, this factor decreases to
about 50 (for the case of Am + Cm targets) or 30 (targets loaded with Am alone). Such reduction
factors, though moderate, already represent sensible improvements of the waste storage conditions.
The flexibility of the concept is an advantage. The research might be first focused on Am target
irradiation without reprocessing. It could progressively encompass the addition of Cm, and later the
target reprocessing.
A problem remains the integrity of targets with a burn-up as high as 90%. Inert support materials
irradiated so far exhibited a large swelling rate. The concept of particle coated fuel, virtually
non-swelling, deserves to be examined for application to Am targets. Studies on this concept are starting.
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